1. Field of the Invention
This invention is directed to a method for determining the wavelength and pulse length of radiant energy used to anneal amorphous semiconductor regions, or to activate doped semiconductor regions, disposed in contact with crystalline semiconductor substrates. The radiant energy can be generated by a laser, flash-lamp or other relatively intense radiant energy source. The method can also be used to perform activation annealing of doped source and drain regions of integrated transistor devices, for example.
2. Description of the Related Art
In the integrated electronic circuit fabrication industry, ion implantation is often used to introduce dopants of appropriate conductivity type (i.e.,--or p-type) into the source and drain regions of integrated transistors. The implantation of the dopant atoms breaks chemical bonds in the source and drain regions of the integrated transistors and, in some instances, can render such regions amorphous. To obtain proper electrical performance of the integrated transistors, the source and drain regions must be annealed to bring such regions to a relatively crystalline state aligned with the substrate and/or to `activate` such regions by incorporating the dopant atoms into the semiconductor crystalline lattice. One technique for performing annealing uses relatively intense radiant energy from a laser or flash-lamp, for example, to melt and crystallize the amorphous regions, or to heat the doped region sufficiently for activation.
Currently, the wavelength, energy dose and pulse length used for radiant energy annealing are determined largely by trial and error, and little thought has heretofore been given to determining relatively effective wavelength and pulse length for the radiant energy without performing numerous experiments. It would be desirable to provide a method which can be used to derive a wavelength and pulse length appropriate for radiant energy annealing, without the need to perform numerous experiments.
In addition, previous methods typically use energy doses in excess of the dose necessary to anneal an integrated device. The excess energy can damage the integrated device by overheating its components or by diffusing dopants beyond safe boundaries to create leakage paths. It would therefore be desirable to provide a method that can minimize, or at least reduce, the amount of energy required to anneal a semiconductor region, relative to previous methods.
In addition, improvement in the determination of the wavelength and pulse length of the radiant energy used for annealing an integrated device and/or circuit would generally permit enhancement of the process margin, leading to relaxed constraints on the materials and process steps used in integrated device or circuit fabrication processes, as well as improvement in the yield of properly functioning integrated devices and circuits, relative to previous methods.